Magna-Tiles Classic 32-Piece Set
If you buy one thing on this list, buy these. Magna-Tiles are the rare open-ended toy a five-year-old grows into rather than out of — at four they laid flat mosaics, at five they start engineering boxes, garages, and ramps, and by seven they're building marble runs. The magnets are strong enough that a real structure holds together, which is the whole game: a tower that collapses every ten seconds kills the play. The genuine tiles cost more than the look-alikes, and the difference is the magnets — the cheap ones give up and frustrate. Start with the 32-piece set; you can always add more.
Builds: spatial reasoning · early geometry · planning
~$40· See it on Amazon